Crosslinked chloroprene/diester polymer

ABSTRACT

A crosslinked copolymer of chloroprene and a diester of an unsaturated carboxylic acid, a composition comprising said crosslinked copolymer and a benzene-soluble chloroprene and process for producing the same.

United States Patent 1 Jennes et al.

[ 1 March 6, 1973 CROSSLINKED CHLOROPRENE/DIESTER POLYMER [75] Inventors: Gert Jennes, Cologne-flittard; Ed-

mund lluther, Oplanden; Willi Wolff, Schildgen, Germany [73] Assignee: Bayer Aktiengesellschaft, Leverkusen, Germany [22] Filed: Feb. 19, 1971 [21] Appl. No.2 117,058

Related U.S. Application Data [62] Division of Ser. No. 728,350, May 10, 1968.

[30] Foreign Application Priority Data June 6, 1967 Germany ..F 52 611 [52] U.S. Cl......260/86.3, 260/29.7 D, 260/33.6 UA,

260/41.5 R, 260/92.3, 260/890 [51] Int. Cl. ..C08f 15/26 [58] Field of Search ..260/86.3

Primary Examiner-Harry Wong, Jr. Att0rney-Connolly & Hutz [5 7] ABSTRACT A crosslinked copolymer of chloroprene and a diester of an unsaturated carboxylic acid, a composition comprising said cross-linked copolymer and a benzenesoluble chloroprene and process for producing the same.

3 Claims, No Drawings CROSSLINKED CHLOROPRENE/DIESTER POLYMER CROSS-REFERENCE TO RELATED APPLICATION This application is a division of application Ser. No. 728,350 filed May 10, 1968.

Benzene-soluble chloroprene polymers and crosslinked chloroprene polymers are known. For example, a benzene-soluble polymer can be obtained by polymerizing chloroprene (2-chloro-l,3-butadiene) in emulsion in the presence of regulators, emulsifiers and activators at temperatures of around 40C and with a monomer conversion of less than 70 percent. The production of such polymers is described in detail, for

example, in U.S. Pat. Nos. 1,950,436; 2,227,517; 2,321,693; 2,371,719; 2,463,225; 2,481,044; 2,494,087; 2,567,117; 2,576,009; 2,831,842;

2,914,497; 2,467,769 and 3,147,3 1 8. If polymerization is continued to monomer conversion rates of more than 90 percent, or is carried out in the absence of regulator s, crosslinked polymers, insoluble in benzene, are obtained (U.S. Pat. No. 3,147,317).

Crosslinked polymers are obtained at polymerization temperatures above 75C, even with fairly low monomer conversions (cf. British Patent Specification No. 1,052,581).

These crosslinked chloroprene polymers are usually employed in admixture with benzene-soluble chloroprene polymers (cf. U.S. Pat. No. 3,147,318).

It has now been found that a readily processed polychloroprene mixture can be obtained by mixing a. a crosslinked chloroprene polymer obtained by copolymerizing chloroprene and at most 20 percent by weight, based on chloroprene, of a diester of a dihydric alcohol containing from two to 10 carbon atoms and an acrylic acid in aqueaus emulsion to form a copolymer latex,

b. a latex of a benzene-soluble polychloroprene in a ratio by weight of from 1:4 to 4:1, based on solids in the latex, and

c. coagulating the resulting mixture in a manner known per se.

The crosslinked chloroprene polymers (a) are prepared by copolymerizing chloroprene and at least 2 and at most 20 percent by weight of a diester of a dihydric alcohol and an acrylic acid in aqueous emulsion. Compounds corresponding to the general formula.

II R 0 R2 in which R and R each represents a hydrogen or chlorine atom or an alkyl radical with from 1 to 4 carbon atoms, and X represents a bivalent aliphatic radical (e.g. bivalent alkyl) with from two to carbon atoms, are particularly suitable for use as the diester of a dihydric alcohol with an acrylic acid. In other words, it is essential that the two ethylenically unsaturated double bonds in this compound should be separated from one another by at least six atoms. Examples of suitable diesters corresponding to this formula include ethylene dimethacrylate, propylene dimethacrylate, butylene dimethacrylate, isobutylene dimethacrylate, ethylene diacrylate, propylene diacrylate, butylene diacrylate and isobutylene diacrylate.

The polymerization process is carried out in a manner known per se. Any of the conventional emulsifiers may be used, including, for example, water-soluble salts, in particular alkali metal or ammonium salts of long-chain fatty acids, resin acids, disproportionated abietic acid, aryl sulphonic acids and their formaldehyde condensation products, alkyl and aralkyl sulphonates or sulphates, oxethylated alcohols or phenols.

Polymerization is carried out in the presence of conventional catalysts that form free radicals, for example, hydrogen peroxide, cumene hydroperoxide, watersoluble salts of peroxy disulphuric acid or 2,2'-azo bis- 2-methyl proprio-nitrile. As a rule, the aqueous solution of the catalyst is introduced into an aqueous emulsion containing the monomers and the emulsifier. In general, polymerization is carried out at a pl-I-value of from 7 to 13 and at a temperature of from 0 to 60C, the emulsion being adjusted in such a way that its total monomer content makes up between 40 and percent of the total weight of the emulsion.

Polymerization may be terminated by the usual polymerization terminators, and any excess monomer may be removed by steam distillation. Details on the procedure, catalysts, terminators may be seen from the patents referred to above.

The latices of the benzene-soluble chloroprenes and their preparation are known from the patents mentioned earlier on, which are incorporated herein by reference.

After the two polymer latices have been mixed together, they are coagulated preferably by low-temperature coagulation, and the resulting coagulate is dried.

The polymers obtained by admixture of crosslinked and benzene-soluble polychloroprenes showed better processing properties than the benzene-soluble polymers. Thus, mixtures prepared from them show a greatly reduced tendency to swell on injection, greater dimensional stability and higher stability under load than corresponding mixtures obtained from the benzene-soluble polymers alone.

EXAMPLE 1 A crosslinked polychloroprene is prepared as follows: The following components are introduced into a 40 liter capacity autoclave which is equipped with stirring mechanism, thermometer and inlets and which is connected to a cooling system.

14.4 liters of desalted water, 815 g of the sodium salt of a disproportionated abietic acid mixture, 72 g of a condensation product of alkyl napthalene sulphonic acid and formaldehyde, 36 g of sodium hydroxide,'60 g of tetra sodium pyrophosphate.

A solution containing the following constituents is equivalent to a monomer conversion of around 77 percent, polymerization is stopped by the addition of a stabilizer solution containing the following constituents:

five g of phenothiazine, g of p-tert.-butyl pyr'ocatechol, and 500 g of benzene. Any unreacted monomers are then removed from the latex. 26.3 kg of an approximately 38 percent by weight latex are obtained. Polymerization may also be carried out continuously, in which case the aqueous phase, the monomer phase and the catalyst solution are pumped separately into the polymerization vessel.

The latex obtained in accordance with Example 1 is mixed with a polychloroprene latex which may be obtained in the usual way from chloroprene by emulsion polymerization, and which contains a benzene-soluble polychloroprene (Example 4). The latex mixture may be worked up in the usual way by low-temperature coagulation and drying.

EXAMPLE 2 1,380 g of ethylene dimethacrylate are used in place of the butylene dimethacrylate of Example 1. Twentysix kg of an approximately 38 percent by weight latex are obtained, which is mixed and worked up as described in Example 1.

EXAMPLE 3 1,380 g of diisopropenyl benzene are used instead of the butylene dimethacrylate of Example 1. Around 26 kg of an approximately 38 percent by weight latex are obtained which is mixed and worked up as described in Example 1.

EXAMPLE 4 Benzene-soluble polychloroprene is prepared by known methods in the presence of regulators, stopping polymerization at a monomer conversion of less than 70 percent and working up the resulting product as described in Example 1.

The mixtures obtained in accordance with Examples 1, 2, 3 and 4 are then blended in the usual way on mixing rolls with the following components:

100 parts by weight of polychloroprene, 29 parts by weight of semi-active furnace soot, 0.5 parts by weight of stearic acid, 2 parts by weight of phenyl-B- 4 naphthylamine, 4 parts by weight of magnesium oxide, 5 parts by weight'of zinc oxide, and 0.5 parts by weight of ethylene thiourea.

Vulcanization is carried out for 30 minutes at 151C. The vulcanizates obtained in this way, and the mixtures, show the following properties when tested:-

TABLE I Mixture of a soluble chloroprene and 2-20 percent by weight of an ester of the formula Hc=0 H3 0 -X-0-(|f 0=GHQ wherein R and R are hydrogen, chlorine or alkyl containing from one to four carbon atoms and X is a divalent aliphatic radical containing two to 10 carbon atoms and wherein the two ethylenically unsaturated double bonds of said formula are separated from one another by at least six atoms.

2. The crosslinked copolymer of claim 1 wherein said ester of said formula is selected from the group consisting of ethylene dimethacrylate, propylene dimethacrylate, butylene dimethacrylate, isobutylene dimethacrylate, ethylene diacrylate, propylene diacrylate, butylene diacrylate and isobutylene diacrylate.

3. The crosslinked copolymer of claim 1 wherein said ester of said formula is butylene dimethacrylate. 

1. A crosslinked copolymer consisting of chloroprene and 2-20 percent by weight of an ester of the formula wherein R1 and R2 are hydrogen, chlorine or alkyl containing from one to four carbon atoms and X is a divalent aliphatic radical containing two to 10 carbon atoms and wherein the two ethylenically unsaturated double bonds of said formula are separated from one another by at least six atoms.
 2. The crosslinked copolymer of claim 1 wherein said ester of said formula is selected from the group consisting of ethylene dimethacrylate, propylene dimethacrylate, butylene dimethacrylate, isobutylene dimethacrylate, ethylene diacrylate, propylene diacrylate, butylene diacrylate and isobutylene diacrylate. 